Geologic Time & the Geologic Time

Scale

Rock Units:Supergroup Group Formation Member Bed

Time Units:Eon Era Period Epoch Stage

How do we make sense out of a 1000 foot-thick

rock sequence?

Geologic Time as a Linear Progression

Geologic Time in one Hour

Hadean – Proterozoic eons Proterozoic & Phanerozoic eons

Evolution of Life on Earth (in 1 hour)

Earth’s Geologic Time in 100 Yards

Phanerozoic Eon begins between 12 and 11 yard lines

Geologic Time as a Spiraling Line

2009 Geologic Time Scale

Subdividing 4.6 billion years into smaller, more “manageable” intervals

Time-rockEon EraPeriodEpochAge

Eonothem ErathemSystemSeriesStage

PhanerozoicCenozoicNeogeneEoceneBartonian

Time vs.

RocksUpper

vs.Late Fossils

EoceneTime vs.

Don’t mix time units with rock units!

Meaning: Late Eocene fossils are found in Upper Eocene rocks.

So Periarchus lyelli (sand dollar) lived during the Priabonian age and fossils occur in rocks from the Priabonian stage.

Pennsylvanian rocks in SE Kansas

Time Units

Time-Rock and Rock-Rock Units

What’s in a Name?

Paleozoic rocks of Europe Western England

Evolution of Western Interior Seaway, North America (Cretaceous Period)

1980s

2009 Cenozoic Era – goodbye Tertiary, hello Paleogene/Neogene

Subdivisions were based on fossil content…

If the type section for the Ordovician is in western England, how do we know rocks in Eastern

USA are the same age?

…Relative dating and Biostratigraphy

Stratigraphic Correlation Through…

Index fossils are:• Common• Widespread• Lived during a relatively short interval of time

Surface Geology of South Carolina